Whilst water from Bucket of Water and Waterskins of Water are the easiest way to get your villagers to satisfy their thirst requirements I will point out that there are a lot of food and drink items that the NPCs can consume to satisfy their water needs - from food (Eg soup, plums etc) and drink (Eg apple juice, mead, rye beer.) More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.